Disturbance Rejection Control With Voltage Constraint for Electro-Hydraulic System Involving Unknown Dead-Zones and Drastic Supply Pressure Variation

In the article, we use the proportional directional valve (PDV) with unknown dead-zones to regulate the electro-hydraulic system (EHS) which has parametric uncertainties including the drastic supply pressure variation; moreover, the external disturbance occurs when the EHS works; in addition, the control voltage applied to the PDV is expected to satisfy the prescribed bound. All of these factors make controller design a challenging problem. The unknown dead-zones, the external disturbance, the drastic supply pressure variation and other parametric uncertainties are viewed as a total disturbance which can be estimated by the linear extended state observer (LESO). Furthermore, a novel robust disturbance rejection position controller with voltage constraints is proposed to compensate for the dead-zones and improve the tracking performance of the EHS regulated by the PDV when the drastic supply pressure variation and the external disturbance occur. The stability analysis is given to ensure that the tracking error of the closed-loop EHS regulated by the proposed controller can converge to the arbitrarily small neighborhood of the origin. Experiments are carried out to verify the effectiveness of the proposed control method. Comparative experimental results demonstrate that the proposed controller can make the load follow the reference trajectory accurately in the presence of the unknown dead-zones and the external disturbance when the supply pressure varies drastically.